The Hydrologic or Water Cycle

Nearly all of the water on Earth is saltwater. Less than 3 percent is fresh waterWater that is relatively free of salts. and most of this is locked up in glaciersa large body of ice with definite lateral limits, which moves in a downslope direction due to its great mass, as in Alaska. and polar ice caps. Less than 1 percent of the world’s water is fresh water available for human and nature’s use.

The water on Earth is continuously circulating between the air or atmosphere, the land and the sea. The ways in which water moves around, above, on and within the Earth is the hydrologic or water cycle. The sun is the energy source for the water cycle, causing water to evaporate from lakes, rivers and oceans, as well as from land surfaces and vegetation. When water evaporates, it changes to a gas (water vapour) and rises in the air. When the water vapour rises and meets cold air, it condenses, forming water droplets, or what we see as clouds or fog. This process is called condensationCondensation is the change of state from a gas to a liquid. Water vapor in the air changes to liquid as it cools. . Water droplets combine into water drops and return to the Earth as precipitation

1. Is any aqueous deposit, in liquid or solid form, that develops in a saturated atmosphere (relative humidity equals 100 %) and falls to the ground generally from clouds. Most clouds, however, do not produce precipitation. In many clouds, water droplets and ice crystals are too small to overcome natural updrafts found in the atmosphere. As a result, the tiny water droplets and ice crystals remain suspended in the atmosphere as clouds.
2. The state of being precipitated from a solution.

Exactly how clouds produce rain has eluded meteorologists until recently. In 1999, Dutch scientists using a supercomputer to model cloud behaviour announced that rain is produced when whirling masses of water, a few centimetres in diameter, force water droplets outward by centrifugal force. These droplets then collide and grow. To fall to the ground as precipitation

1. Is any aqueous deposit, in liquid or solid form, that develops in a saturated atmosphere (relative humidity equals 100 %) and falls to the ground generally from clouds. Most clouds, however, do not produce precipitation. In many clouds, water droplets and ice crystals are too small to overcome natural updrafts found in the atmosphere. As a result, the tiny water droplets and ice crystals remain suspended in the atmosphere as clouds.
2. The state of being precipitated from a solution.

Some rain is absorbed by vegetation or evaporates before it reaches the ground. Some evaporates after it reaches the surface. Some soaks into the ground and is taken up by the roots of plants and then released back into the air through the leaves of the plants in a process called transpiration. The combination of evaporationEvaporation can be defined as the process by which liquid water is converted into a gaseous state. Evaporation can only occur when water is available. It also requires that the humidity of the atmosphere be less than the evaporating surface (at 100 % relative humidity there is no more evaporation). The evaporation process requires large amounts of energy. For example, the evaporation of one gram of water at a temperature of 100° Celsius requires 540 calories of heat energy (600 calories at 0° Celsius). and transpirationTranspiration is the process of water loss from plants through stomata. Stomata are small openings found on the underside of leaves that are connected to vascular plant tissues. Some dry environment plants do have the ability to open and close their stomata. Transpiration is a passive process largely controlled by the humidity of the atmospheric and the moisture content of the soil. Of the transpired water passing through a plant only 1 % is used in the growth process. Transpiration also transports nutrients from the soil into the roots and carries them to the various cells of the plant. is referred to as evapotranspirationCombined loss of water to the atmosphere via the processes of evaporation and transpiration . Some rain soaks beneath the water tablein an aquifer, it is the upper surface of the zone of saturation under unconfined conditions; water in the rocks is at atmospheric pressure. into underground units of water-bearing rock called aquifers. The remainder becomes surface or stormwater runoff that flows over the ground to wetlands, lakes, ponds, rivers and oceans. A water molecule’s trip from the atmosphere and back may be very long or very short. It may stay in the atmosphere for only a few days or it may remain deeply buried in cavities in the earth or frozen in polar ice caps for thousands of years.

The Water Cycle in Florida

No significant amount of water enters or leaves the global water cycle. The water cycle in Florida, however, is an open system. Florida’s water cycle includes the flow of surface water and ground water from Georgia and Alabama into northern and northwestern Florida, as well as outflows to the Atlantic Ocean and the Gulf of Mexico. Hydrologist Garald Parker was the first to discover that neither surface water nor ground water crosses a line snaking across the peninsula from Cedar Key on the Gulf to New Smyrna Beach on the Atlantic (Betz 1984). This line is known as the hydrologic divide. South of the hydrologic divide, Florida is an island as far as fresh water is concerned: it totally depends on rainfall for its fresh waterWater that is relatively free of salts. , including ground water stored in aquifers. North of the hydrologic divide, Florida receives water from outside the state.

An average of 150 billion gallons of rain falls each day in Florida. Another 26 billion gallons flows into the state, mostly from rivers originating in Georgia and Alabama making a total of 176 billion gallons. Nearly 70 percent of the rain (107 billion gallons) returns to the atmosphere through evaporationEvaporation can be defined as the process by which liquid water is converted into a gaseous state. Evaporation can only occur when water is available. It also requires that the humidity of the atmosphere be less than the evaporating surface (at 100 % relative humidity there is no more evaporation). The evaporation process requires large amounts of energy. For example, the evaporation of one gram of water at a temperature of 100° Celsius requires 540 calories of heat energy (600 calories at 0° Celsius). and plant transpirationTranspiration is the process of water loss from plants through stomata. Stomata are small openings found on the underside of leaves that are connected to vascular plant tissues. Some dry environment plants do have the ability to open and close their stomata. Transpiration is a passive process largely controlled by the humidity of the atmospheric and the moisture content of the soil. Of the transpired water passing through a plant only 1 % is used in the growth process. Transpiration also transports nutrients from the soil into the roots and carries them to the various cells of the plant. (evapotranspirationCombined loss of water to the atmosphere via the processes of evaporation and transpiration ). The remainder flows to rivers or streams or seeps into the ground and recharges aquifers. Each day in Florida, 2.7 billion gallons are incorporated into products or crops, consumed by humans or livestock, or otherwise removed from the immediate environment (consumptiveOf or pertaining to consumption; having the quality of consuming or dissipating. Consumptive uses of water include pumping water for irrigation or municipal uses, and evapotranspiration. use). Source: Fernald and Purdum 1998.